The kingpin of standardised semi-trailers is provided to engage separately on a fifth wheel carried by a towing vehicle in order to form a pivot link allowing semi-trailers to be moved by the towing vehicle associated therewith.
Known from patent EP 1874607, in the name of the applicant, is a system of locking the kingpin of a semi-trailer on a railway unit in which a cowling part is mounted, by a central opening, on the kingpin of semi-trailers in order to be received in a receiving element, called nacelle, which is mounted on the railway unit. This nacelle is in particular intended to automatically center and lock the cowling part, along with the kingpin, when the cowling part is received within the nacelle. This nacelle is normally moved by a lifting means enabling the nacelle to be moved vertically to receive the cowling part and the kingpin in order to hold and lock them. This lifting means normally comprises a jack screw unit intended to support the vertical load of the semi-trailer.
According to this prior kingpin locking system, the nacelle is pivotally mounted on a support unit composed of a link table resting flat on the railway structure in order to provide stability to the nacelle around the roll axis. This link table is pivotally mounted, articulated at its rear end onto the railway structure so as to be free in longitudinal articulated movements and for pivoting upwards. This articulated structure for linking the nacelle to the railway structure gives the link table sufficient articulation for longitudinal and vertical movements with respect to the railway structure to enable the nacelle to be raised and lowered.
In the event of buffering shock of the railway unit carrying the semi-trailer, or during other events, the railway unit receives a violent impact. Because the nacelle is connected to the support unit, which allows free longitudinal travel movements, the impact is transmitted to the locking system and to the kingpin.
Currently, the locking system, although very strong, does not meet railway standards and is susceptible to being damaged by such a shock, which can be equivalent to a force of several tens of tons. Indeed, the means of raising the nacelle generally comprises a vertical jack screw designed to withstand loads and vertical shocks, but is vulnerable to bending forces and horizontal shocks.
In effect, according to the prior kingpin locking system, the lifting means is fixedly mounted on the railway unit and it therefore sustains a large part of the longitudinal shock in the event of buffering shock.
Similarly, at the cowling part, a shock risks damaging the kingpin because it meets road standards, which are less demanding than railway standards on this point.
Possible damage to a locking system or kingpin is not easily detectable after a shock. Thus, after a violent shock during a buffering shock, these elements can be weakened without this being detected. Thus, the operators loading and unloading trailers on the railway unit may continue doing their work without being aware of this weakness, which can have serious consequences.
Indeed, if the locking system is defective during railway transport of a semi-trailer, that semi-trailer is likely no longer to be immobilized on the railway unit and could fall from it.
In the case of a weakened kingpin, when the driver, after having unloaded the semi-trailer from the railway unit, takes it to its final destination by towing it with his tractor, the kingpin is likely to break during travel and the semi-trailer can turn over on the road, with tragic consequences.
There is therefore a need for a device intended to ensure the structural integrity of the locking system, which must allow a certain tolerance to the stresses experienced during operation under normal situations. Thanks to such a device, the locking system can advantageously meet railway standards.
Optionally, in the event of buffering shock of the railway unit or other shocks likely to damage the locking system or the kingpin, there is also a need for a shock detection device that makes it possible to detect whether the railway unit carrying the semi-trailer has undergone a shock likely to damage the kingpin.
These different devices must advantageously be able to be calibrated in order to be triggered beyond a predetermined shock threshold. Depending on the operating requirements, this threshold can be modified to allow detection of weaker shocks, particularly with a desire to protect transported merchandise, or heavier shocks, for example in the case of different railway standards.